The purpose of this project is to attempt the synthesis of a full-size DNA copy of simian sarcoma virus RNA in an endogenous reverse transcriptase reaction. BIBLIOGRAPHIC REFERENCES: Robert-Guroff, M., Schrecker, A. W., Brinkman, B. J. and Gallo, R.C.: DNA polymerase gamma of human lymphoblasts. Biochemistry (In press, 1977). Henderson, G. B., Schrecker, A. W., Smith, C., Gordon, M., Zevely, E. M., Vitols, K. S. and Huennekens, F. M.: Transport of methotrexate and other folate compounds: components, mechanism and regulation by cyclic nucleotides. Adv. Enzyme Regul. (In press, 1977).